Randomized, controlled, double-blind clinical trial to investigate whether supplemental enteral glutamine in infants with gastrointestinal disease will improve clinical outcomes, and whether Gln supplementation alters mucosal protein synthesis rates and/or genetic expression of proteins possibly involved in intestinal adaptation. Hypotheses: - Enteral supplementation with the amino acid L-glutamine in infants with gastrointestinal disease will improve intestinal adaptation and absorption of macronutrients. - Glutamine supplementation will be associated with increased gastrointestinal mucosal protein synthesis rates. - Expression of mRNAs for insulin-like growth factor-1 (IGF-1), and IGF-1 binding proteins-3 and -4 (IGFBP-3 and -4) are regulated by glutamine supplementation after intestinal resection. Aims: - To evaluate the clinical efficacy of supplemental dietary L-glutamine in infants with significant gastrointestinal disease. - To measure mucusal protein synthesis rates in infants undergoing gastrointestinal surgery, and to investigate the effects of glutamine supplementation on this index of gut adaptation. - To measure intestinal mucosal gene expression of insulin-like growth factor-1 (IGF-1), and IGF-1 binding proteins-3 and -4 mRNA in infants undergoing intestinal surgery, and to investigate the effects of Gln supplementation on the cellular expression of these genes.